In the manufacture of synthetic-resin foil or sheet bags (plastic) bags, the synthetic-resin material is usually blown to produce a foil or sheet which is flattened and sealed along various edges to produce individual bags which can be separated from the continuous extruded material and packaged or assembled for distribution or use.
One of the principal forms of distribution is an assembly of such bags in a stack in which the bags are generally interconnected along one edge, i.e. in a pad or a block from which individual bags may be removed for use, as proposed in German patent document (Auslegeschrift) DT-AS No. 2,141,045.7. To interconnect the bags by means of heated welding mandrels or pins, as described in U.S. Pat. No. 3,021,947, has required the formation of a fusing or fastening strip along one end of each bag, a bag being removed from a stack by tearing along a line of perforations defining the fusing strip. Such strips represent a waste of synthetic resin, which waste is particularly costly in times of scarcity of raw materials. Scarcity induces the production of thinner-walled plastic bags which have a relatively small slope or inclination when stacked.
In German Open Application (Offenlegungsschrift) DE-OS No. 2,418,233.0-27, a proposal for simplifying the interlocking or connection of bags includes a machine having clamping bars, a separate needle bar and another bar for carrying the heating elements. The bags are joined to one another via respective welding strips extending the breadth of the bags and separable therefrom along a line of perforations.
It has been proposed to connect the bags at fusing areas or sections located at the corners or in the middle of an edge of the plastic bags, the connection being implemented by means of the afore-mentioned heating or welding pins. In known devices for thermally bonding the bags at such localized fusing areas, the bags are initially placed in stacks and then bonded by the welding pins and perforated by punches. Owing to the thinness of the plastic bags, another method for forming the bag pads has not been conceived until now. For this reason the description in U.S. Pat. No. 3,021,947 is sketchy and includes no apparatus utilizing the proposed welding pins.